Generally, an ultrasonic sensor is provided with a sensor body, which has an ultrasonic transducer and is attached to a bumper of a vehicle. The ultrasonic transducer generates ultrasonic wave. By receiving reflection wave of the ultrasonic wave, an obstacle near the bumper is detected.
For example, with reference to JP-2003-9270A (U.S. Pat. No. 6,759,950), FIG. 12 is a partially sectional view showing a mounting construction for fixing a conventional ultrasonic sensor 100 to a bumper 101. As shown in FIG. 12, a sensor body 102 of the ultrasonic sensor 100 has a circular column shape. By inserting the sensor body 102 in a circular hole 101a arranged at the bumper 101 from the outside of the bumper 101, the sensor body 102 is fixed to the bumper 101.
Specifically, the sensor body 102 has a flange 102a which is positioned at the rear end thereof in the insertion direction of the sensor body 102 to the bumper 101. A V-shaped metal spring 103 is provided around the outer periphery of the sensor body 102.
Thus, when the sensor body 102 is inserted through the hole 101a of the bumper 101, the expanding force in the diameter direction of the sensor body 102 generated by the metal spring 103 is applied to the wall face constructing the hole 101a of the bumper 101, in such a state that movement in the insertion direction of the sensor body 102 is regulated by the flange 102a. Thus, the sensor body 102 is substantially fixed to the bumper 101.
In recent years, the ultrasonic sensor is becoming intelligent, and a circuit board on which not only the ultrasonic transducer but also a signal processing circuit and the like are arranged is being housed in the sensor body. Thus, the sensor body is enlarged, and there occurs a problem that the sensor body cannot be inserted through the hole of the bumper from the outside of the bumper. Therefore, it is necessary to fix the ultrasonic sensor to the bumper by a structure different from the conventional structure.
In order to solve the above-described problem, the following construction is considered by the inventors of the present invention. That is, with reference to FIG. 13, a bezel 4 (cover) which has a cylindrical shape and has a flange 4a at one end thereof is provided. The bezel 4 is inserted from the outside of a bumper 2 into a hole 2a of the bumper 2, to be fixed to the bumper 2. Thereafter, a circular column portion in which an ultrasonic transducer of the sensor body 3 is disposed is inserted in a hollow portion of the bezel 4 from the inside of the bumper (that is, in direction opposite to insertion direction of bezel 4 to hole 2a of bumper 2), so that the sensor body 3 is fixed to the bumper 2 via the bezel 4.
In this case, because it is necessary to hold the sensor body 3 having a large size at the bezel 4 which functions as a fixing member, the bezel 4 is to be firmly fixed to the bumper 2 and the sensor body 3 is to be firmly fixed to the cover member 4.
Therefore, as shown in FIG. 13, it is proposed by the inventors of the present invention to provide a snap fit 4b, a nail portion 3z, a lance 38 and a hole portion (not shown) which is engaged with a nail portion 38b of the lance 38 and positioned at the upper side (with respect to up-down direction of drawing of FIG. 13) of the bezel 4. In this case, the snap fit 4b has a hole portion (not shown) positioned at the lower side (with respect to up-down direction of drawing of FIG. 13) of the bezel 4. The nail portion 3z is engaged with a hole portion 4z of the snap fit 4b, and positioned at the lower side of the sensor body 3. The lance 38 which is provided with the nail portion 38b is positioned at the upper side of the sensor body 3.
In this case, when the sensor body 3 is fixed to the bezel 4, the nail portion 38b of the lance 38 contacts the outer surface of the side wall of the bezel 4 so that the lance 38 is elastically deformed. When the nail portion 38b of the lance 38 comes to the hole portion of the bezel 4, the shape of the lance 38 recovers so that the nail portion 38b enters into the hole portion. Thus, the nail portion 38b is engaged with the hole portion.
Similarly, the snap fit 4b is pressed by the nail portion 3z of the sensor body 3 to be elastically deformed. When the hole portion 4z of the snap fit 4b comes to the nail portion 3z, the shape of the snap fit 4b recovers so that the nail portion 3z enters the hole portion 4z. Thus, the nail portion 3z and the hole portion 4z are engaged with each other. Thus, the bezel 4 and the sensor body 3 can be further firmly fixed via the lance 38, the snap fit 4b and the like.
However, in the above-described construction, as indicated by the arrow in FIG. 13, an elastic reaction force of the lance 38 is applied to the bezel 4 in a direction facing the lower side, and a force pressing the snap fit 4b by the nail portion 3z is applied in a direction facing the lower side. Therefore, the two forces are applied to the bezel 4 in the same direction. Thus, the cover member 4 is susceptibly slanted.
Similarly, there also occurs the problem in the case where the ultrasonic sensor is mounted to a vehicle component other than the bumper.